Can I Build a New Home in My Garden?

Residential gardens, side plots and underused areas of land can sometimes accommodate an additional dwelling. There is no general prohibition on garden development, but a successful proposal must establish the principle of development and demonstrate that a new home can be accommodated without unacceptable planning harm.

Building a new home within a residential garden can be an effective way of unlocking the value of land already in ownership. It may provide a new home for a family member, create a property for sale or rent, or enable a landowner to make more efficient use of an unusually large residential plot.

However, garden development – sometimes referred to as backland development, infill development or, less favourably, “garden grabbing” – can raise a number of planning issues which should be understood before a scheme is progressed.

This guide considers the principal planning issues affecting garden land development, with particular focus on the revised National Planning Policy Framework and the implications of Policies S4, S5 and L2.

Is the garden large enough to build another house?

There is no single national minimum garden size required to build a new home. In addition to the building itself, a proposal may need to provide space for private amenity, bin and cycle storage, parking, vehicle manoeuvring, access and landscaping.

These requirements all affect the amount of land needed. Nevertheless, a comparatively modest plot can sometimes accommodate a sensitively designed new dwelling, particularly where the surrounding area already contains similarly sized plots or a denser pattern of development.

The assessment will normally take account of:

• the size and shape of the site
• the position of the existing house
• access into the site
• the size and design of the proposed dwelling
• neighbouring properties
• the character and density of the surrounding area
• private garden space
• parking requirements
• trees and landscaping
• other environmental or planning constraints

The development capacity of garden land is therefore highly site-specific and cannot be determined by plot size alone. Where the position is uncertain, a planning feasibility study or site appraisal can establish the principal policy and site constraints before substantial design costs are incurred.

Is garden land considered previously developed land?

Many national and local planning policies seek to make effective use of previously developed, or brownfield, land. There can therefore be planning benefits where a site falls within the definition of previously developed land.

However, not all residential garden land is treated as brownfield land.

The glossary to the NPPF excludes land in built-up areas such as residential gardens from the definition of previously developed land. The application of a previous, but similar, definition was considered by the High Court in 2018, where the distinction between residential gardens within and outside a built-up area was material.

Accordingly, where brownfield status is relevant to the planning strategy, it is important to establish the physical context of the site rather than assume that all garden land is treated in the same way.

My garden land is inside the settlement boundary. Can it be developed?

In many cases, development within an established settlement will be more straightforward in principle than development outside it. Policy S4 of the revised NPPF states that development proposals within settlements should be approved unless the benefits of doing so would be substantially outweighed by adverse effects when assessed against the relevant policies of the Framework.

Policy S4 also identifies circumstances where those adverse effects may outweigh the benefits. Of particular relevance to garden land development is the application of Policy L2(1)(d), which relates specifically to development within residential curtilages.

Policy L2 therefore has an important role in the assessment of garden development and is considered in more detail below.

Other matters including heritage, residential amenity, biodiversity, flood risk, highways and local character will also influence the acceptability of a proposal.

Development outside settlements

Policy S5 of the NPPF has significant implications for development outside settlements.

It is important to note that the concept of a settlement is not necessarily the same as a defined settlement boundary. The physical relationship between a site and existing development may therefore be relevant alongside any development plan designation.

Policy S5 identifies certain forms of development which should be approved outside settlements unless the benefits would be substantially outweighed by adverse effects.

Of particular relevance to garden land developers is criterion (e), which provides support for limited infilling within groups of houses. The key questions are likely to include what constitutes “limited” development and whether the proposal can properly be described as infill.

The policy also identifies other potential routes to development, including:

• the redevelopment of previously developed land;
• development within reasonable walking distance of a well-connected station; and
• development which would address an evidenced unmet need, where it is physically well-related to an existing settlement and the scale of development can be accommodated having regard to the availability of infrastructure.

Paragraph 4 of Policy S5 states that proposals which do not fall within one of the identified categories should only be approved in exceptional circumstances where the benefits would substantially outweigh the adverse effects, including effects on countryside character and sustainable patterns of movement.

For garden land outside settlements, identifying the correct policy route before progressing an application is therefore particularly important.

Policy L2 of the NPPF and its implications

Policy L2 of the NPPF is likely to be a key consideration for many garden development projects. In broad terms, the policy requires substantial weight to be given to making effective use of land and identifies a number of circumstances in which additional development should be supported.

Of particular importance, criterion (d) states that significant weight should be given to creating additional homes within settlements through the use of airspace above existing premises, sensitive redevelopment or additional development within existing plots.

The policy then establishes a number of requirements which developers and landowners need to take into account.

Development should be consistent with the overall street scene, except where larger buildings would be appropriate or where the development would not be visible from the street. Policy L2 also requires safe access and egress and acceptable living standards for both future occupiers and neighbouring properties.

For development involving residential gardens, Policy L2 introduces further requirements relating to the scale of development and the amount of land retained as undeveloped space.

Footprint calculations

Policy L2 states that development involving residential curtilages should not occupy more than twice the footprint of all existing buildings on the site.

The reference to “existing buildings”, rather than simply the existing dwelling, is important. In our view, the wording indicates that the relevant calculation can include other established buildings on the site, such as garages and outbuildings, where they properly constitute existing buildings.

Whilst the drafting could be clearer, the apparent intention is that the footprint of the proposed development can be assessed by reference to the combined footprint of the existing dwelling and other qualifying buildings within the site.

Footnote 38 is also significant because it establishes the relevant date against which “existing buildings” are to be assessed. Buildings constructed after that date would not contribute towards the calculation.

The footprint calculation can have a significant effect on the amount of development capable of being accommodated and should therefore be established at an early stage in the design process.

Retaining 50% of the non-developed area

Policy L2 also requires garden land development to retain at least 50% of the non-developed area within the curtilage of the existing buildings.

This requirement is intended to ensure that residential plots are not developed to an inappropriate extent and that an acceptable balance remains between built development and open land.

The assessment is therefore likely to extend beyond the footprint of the proposed dwelling itself. Consideration may need to be given to private garden areas, parking, access roads, turning areas, hardstanding and other developed parts of the site.

The requirement can consequently have a significant influence on the layout and capacity of a garden development proposal.

Additional development

The first part of Policy L2 places limits on development by reference to both the footprint of existing buildings and the amount of undeveloped land retained within the site. In some cases, these requirements could significantly restrict the amount of development capable of being accommodated.

However, importantly, the policy also provides scope for additional development.

It states that additional development may be acceptable where it can be accommodated without harm to the overall character of the area, while taking into account the availability of infrastructure and the importance of locating development in sustainable locations in accordance with Policy TR3.

This is significant because it indicates that the twice-footprint and 50% requirements should not necessarily be treated as absolute limits in every case.

Where the surrounding area is characterised by a denser pattern of development, smaller plots or existing infill and backland development, there may be a basis for arguing that a greater amount of development can be accommodated without harm to local character.

In these circumstances, the planning assessment is likely to require consideration of surrounding plot sizes, existing development density, the relationship between buildings and gardens, the pattern of development, infrastructure capacity, accessibility and the sustainability of the location.

Accordingly, where a proposal exceeds the standard Policy L2 parameters, the wider character and sustainability of the site may be critical to determining whether additional development can be justified.

Safe access and acceptable living standards

Policy L2 also requires garden land development to provide safe access and acceptable living standards.

From a highway perspective, this will normally require consideration of access width, visibility, pedestrian safety, parking, vehicle manoeuvring and emergency or refuse access. The appropriate standard will depend upon the scale of development and the characteristics of the site.

A single additional dwelling will not necessarily require the same access arrangements as a larger residential scheme, but safe and suitable access must still be demonstrated.

Residential amenity will also be an important consideration. Potential impacts on neighbouring occupiers include overlooking, loss of privacy, loss of daylight or sunlight, and an overbearing relationship.

In many cases, these impacts can be reduced through careful consideration of building height, orientation, window positions, landscaping and separation distances.

The relationship with the existing dwelling on the site must also be considered. Subdivision of a residential garden should not result in the original property being left with an unacceptable standard of amenity or inadequate private garden space.

Living standards for future occupiers

Policy L2 requires an acceptable standard of living to be provided for the future occupiers of the new dwelling. This is likely to include consideration of internal space, natural light, outlook, privacy, private amenity space, noise, bin and cycle storage and parking provision.

Where relevant, development will also need to comply with applicable technical space standards and local design policies.

The objective should be to create a high-quality residential environment rather than simply demonstrate that another building can physically fit within the site.

Other planning considerations

Although Policies S4, S5 and L2 are likely to be central to many garden development proposals, they are not the only relevant considerations. Depending upon the site, an application may also need to address:

• heritage and Conservation Area impacts
• listed buildings
• trees and Tree Preservation Orders
• ecology and protected species
• Biodiversity Net Gain
• flood risk and drainage
• highway safety
• local design policies

For self-build projects, our guide to Biodiversity Net Gain and self-build homes explains the BNG position in more detail.

Assessing the development potential of garden land

There is no general prohibition on constructing an additional dwelling within a residential garden. However, development potential will depend upon the planning policy framework, the location and physical characteristics of the site, its relationship with surrounding development and any environmental or technical constraints.

In many cases, the critical question is not simply whether there is enough physical space for another dwelling, but whether an additional home can be accommodated in a way that is consistent with planning policy and the character of the surrounding area.

Where the principle is supportable, the next stage will normally be to establish the most appropriate design and planning application strategy.

Planning advice for garden land development

Cedar Planning provides independent planning advice to landowners, developers and property owners considering the development of residential garden land.

Our planning feasibility and site appraisal work can consider whether residential development is acceptable in principle, the relevant national and local policies, settlement and countryside policy, the implications of Policy L2, likely site capacity, access and highway constraints, neighbouring amenity, planning history, comparable nearby development and the most appropriate planning strategy.

Early planning advice can help establish the realistic development potential of a site before significant expenditure is incurred on drawings, technical reports or a planning application.

Contact Cedar Planning to discuss the site, or view our planning feasibility and site appraisal service.

Dan Malloy MRTPIDirector and Chartered Town Planner at Cedar Planning, with more than ten years of public and private-sector planning experience. About Cedar Planning